Problem: How many miles can a car travel in 20 minutes if it travels $ \, \frac{3}{4} \, $ as fast as a train going 80 miles per hour?
Answer: The car travels at a speed of $$\frac{3}{4}\times80\text{ miles per hour}=3\times20=60\text{ miles per hour}.$$ In $20$ minutes, the car travels $$\frac{60 \text{ miles}}{60\text{ minutes}}\times20\text{ minutes}=1\times20=\boxed{20\text{ miles}}.$$